The present disclosure relates to semiconductor devices and methods for manufacturing the semiconductor devices. More particularly, the present disclosure relates to a semiconductor device including a Metal Insulator Semiconductor Field Effect Transistor (MISFET) having a gate electrode made of a metal material, and a method for manufacturing the semiconductor device.
As the scale and speed of semiconductor integrated circuit devices increase, an attempt is being made to achieve further miniaturization of MISFETs. The further miniaturization of MISFETs is accompanied by an extremely thin thickness of the gate insulating film, leading to problems, such as manifestation of the depletion capacitance of the polysilicon gate electrode and penetration of boron into the channel region. To solve these problems, a semiconductor device with a dual-metal gate structure has been studied in which a metal gate electrode made of a metal material is used as the gate electrode of an n-type MISFET (hereinafter referred to as an “n-type MIS transistor”), and a metal gate electrode made of a metal material is used as the gate electrode of a p-type MISFET (hereinafter referred to as a “p-type MIS transistor”).
In the case of the dual-metal gate semiconductor device, the gate electrodes of the n- and p-type MIS transistors need to be made of different metal materials. For example, the gate electrode of the n-type MIS transistor is made of a metal material having a work function of 4.05 eV or more and 4.6 eV or less, and the gate electrode of the p-type MIS transistor is made of a metal material having a work function of 4.6 eV or more and 5.15 eV or less.
As a method for manufacturing the dual-metal gate semiconductor device, for example, a first conventional semiconductor device manufacturing method (see, for example, NON-PATENT DOCUMENT 1) and a second conventional semiconductor device manufacturing method (see, for example, NON-PATENT DOCUMENT 2) have been proposed.